As the demand for lithography-based device structures having ever-smaller features continues to increase, the need for improved illumination sources used for lithography and inspection of the associated reticles that lithographically print these ever-shrinking devices continues to grow. One such illumination source, utilized in lithography and inspection systems, is an extreme ultraviolet (EUV) light source.
EUV inspection systems, and especially their optics, need to operate in a clean vacuum environment. However, contaminants that tend to foul the vacuum environment cannot be completely removed from the system. Such is the case, for example, when components of the EUV system, such as adhesives, actuators, and cables, contain unavoidable contamination sources. As a result, the EUV optics, within the vacuum chamber, are exposed to a partial pressure of contaminants, such as hydrocarbons and gas phase H2O. These contaminants, when exposed to the EUV radiation within the tool, will lead to the growth of carbon and/or oxides optical surfaces of the system, such as mirrors. In the case of mirrors, the contamination will cause a reflectivity drop, resulting in a phase change in the light incident upon a given mirror. Both of these effects, if unchecked, will cause a degradation of the optics over time, leading to a failure of the optical system.
Therefore, it is desirable to provide a method and system that cure the defects of the prior art identified above.